The present invention relates to the sphere of packing and packaging. In particular, its subject is an industrial packing for products or materials which can give off volatile vapors or for those on which it is at least desired to confer an odor during the period before their consumption or activation, during which period the product is in closed packaging. It relates for example to cosmetic products, various perfumed products, air fresheners, detergents or fabric softeners, paper, textiles, insecticides, flavourings, foods or tobacco.
As will emerge in more detail in the remainder of this description, the packaging in the invention constitutes a medium capable of diffusing volatile or sanitizing vapours and is therefore generally intended to improve the consumer's perception of the packaged products or materials.
It is undisputed that the odorizing properties of a product often have a determining effect on the consumer. In many cases and for a certain category of products, they define, often unconsciously, the propensity to buy.
Manufacturers have applied themselves to increase this signal by trying to confer or intensify the odorizing characteristics of the products offered for consumption. However, there are obvious, practical limitations. It is actually difficult to increase the odourizing intensity of a product beyond certain limits without having a negative effect on the desired olfactory harmony. In other words, the odor of a product should be perceptible and agreeable and thus confer a distinctive character to the product, without however being overpowering.
Moreover, it is known that the consumer attaches importance to the first impression he receives of a product. The fragrance which is given off from a product which has just been unpacked can have a determining impression regarding acceptance of the product itself. Various solutions are known which consist in perfuming the packaging material and several processes have been suggested for this purpose.
There exists scented packaging materials in the commercial world, is generally consisting of paper, cardboard or plastic. Plastic has been the subject of particular attention. Due to the implementation of the so-called "master-batch" technique, concentrates of perfuming agent are prepared in matrices constituted by the same polymeric resin, generally a polyolefin resin, as that which is used for the preparation of the final product. Products, that products with a polyolefin matix, intended for the "master-batch" process and characterized by a high content of volatile perfuming substances, have recently appeared on the market. These are resins with a low-density polyethylene base (LPDE), of polypropylene and of copolmers of ethylene vinyl acetate (see for example: Polyiff (registered trade mark); origin: Int. Flavors and Fragrance, Inc.).
These polyolefin concentrates are generally prepared by incorporating the perfume in appropriate mixers at temperatures which vary according to the polymeric base. The polyethylene for example is treated at a temperature lying between 80.degree. and 180.degree. C., enabling a viscous mass to be obtained to which the desired perfume is added before cooling and granulation. Such a process meets with a major, practical difficulty, the incorporation of the perfume at a high temperature in fact causes olfactory losses and modifications to some of its constituents, this limiting the choice of suitable perfuming bases.
On the other hand, the perfuming of plastic sheeting also meets with major problems. In fact, the manufature of sheeting is essentially carried out by one of the following methods:
a. extrusion coating PA0 b. sheet die extrusion PA0 c. blown extrusion
In each of these methods, the polymer is subject to a thermal treatment of shorter or longer duration, followed by compression through a nozzle of appropriate geometry. When this compression is accompanied by an injection of air or of an inert gas, and the nozzle has an annular shape, as is the case with blown extrusion, a product is obtained which is in the form of a cylinder whose walls are constituted by the plastic material now reduced to a thin layer of a homogeneous thickness. By cutting lengthways, unilayer or multilayer sheets are then obtained. Now, the perfuming of sheets by means of a perfume concentrate, in the form of master batch, is badly suited to the processes we have just described because in each of the variants mentioned, the perfume is subject to considerable temperature stresses, this causing a denaturation in a good many cases. Moreover, this phenomenon is still more pronounced in the blown extrusion process, where the combined action of the heat and of the current of hot air causes substantial evaporation of the volatile constituents of a purifying base, from the surface of the hot film which is directly exposed to the atmosphere.